The present invention generally relates to semiconductor devices having a ball grid array (BGA) contact structure and more particularly to a so-called micro-BGA device in which a circuit substrate is provided on a semiconductor chip with a size smaller than an outer dimension of the semiconductor chip.
FIG. 1 shows a conventional semiconductor device having a BGA contact structure.
Referring to FIG. 1, the semiconductor device includes a circuit substrate 36 and a semiconductor chip 32 provided on a top surface of the circuit substrate 36. Further, electrodes on the semiconductor chip 32 are electrically interconnected to corresponding electrodes formed on the top surface of the circuit substrate 36 by way of a bonding wire 34. The electrodes on the top surface of the circuit substrate 36 are in turn interconnected to respective corresponding electrodes on a bottom surface of the circuit substrate 36 via through-holes (not shown) provided in the circuit substrate 36. The circuit substrate 36 further carries solder bumps 37 on the bottom surface in correspondence to the electrodes provided thereon. The semiconductor chip 32 on the top surface of the circuit substrate 36 is encapsulated by a resin package body 31 together with the bonding wire 34.
FIG. 2 shows another conventional BGA semiconductor device disclosed in the U.S. Pat. No. 5,148,265.
Referring to FIG. 2, the BGA semiconductor device is distinct over the semiconductor device of FIG. 1 in that a circuit substrate 46 corresponding to the circuit substrate 36 of FIG. 1 is now provided on a top surface of a semiconductor chip 42 corresponding to the semiconductor chip 32, with a size smaller than an outer size of the semiconductor chip 42. Such a BGA device that uses a circuit substrate having an outer size smaller than the outer size of a semiconductor chip is called a micro-BGA device. In the micro-BGA device of FIG. 2, it should be noted that the solder bumps (not shown) are provided on electrodes 43 formed on the circuit substrate 46.
In the foregoing conventional BGA device of FIG. 1, there arises a problem in that, because of the lateral size of the circuit substrate exceeding the size of the semiconductor chip, the overall size of the semiconductor device tends to become excessively large and a high-density mounting of the device on an electronic apparatus is difficult.
In the foregoing micro-BGA device of FIG. 2, on the other hand, it is necessary to bond the circuit substrate, of which size is smaller than a size of the semiconductor chip, on the semiconductor chip, while handling or alignment of such a small semiconductor chip or small circuit substrate is difficult and increases the number of fabrication steps as well as the cost of the semiconductor device.